3 inch for ducks, 3 1/2 for geese. As for the theory of ONLY 2 3/4 inch. That would be great if EVERYone COULD get ALL the birds within range. That would depend on how well one could call, his knowledge of setup, how well the hunter is hidden, etc, etc... Not everyone is as good as the next guy at getting the birds to land in their lap. I'm definately not that good. Probably never will be. I'm learning this waterfowl game as I go. Maybe in thirty of forty years I can get all the birds within range of using only 2 3/4 inch shells, but for now, I'll keep blasting away with my magnum 3 1/2 inchers! If I could get the ALL the birds to fly within range EVERY time, I wouldn't know what to do!
Hey, did you grab the blind bag with the shells when we left the truck?
Safetys, use them: If you can see red, you can get dead!